Langerhans Cell Histiocytosis
• A clonal, neoplastic proliferation of Langerhans cells
Mutations:
• BRAF V600E mutation in -50% of cases
• MAP2K1 mutation in -25% of cases
Clinical Findings:
LCH can affect a variety of sites: bone, skin, oral cavity, lung, lymph node, liver, spleen Formerly separated into 3 types:
- Localized (“eosinophilic granuloma”) -Multifocal (“Hand-Schüller-Christian disease”)
-Systemic (“Letterer-Siwe disease”) Lymphadenopathy, when present, usually occurs in widespread disease
• Cervical nodes are most commonly involved
• Langerhans cells have
ovoid, “coffee bean” nuclei with nuclear grooves/ folds
• Inconspicuous nucleoli
• Thin nuclear membranes Indistinct cytoplasmic borders
• IHC: positive for S100, CD1a, langerin (CD207)
• CD68 is variably positive
• Birbeck granules on EM